Two contact detection jigs are spaced apart and attached on a table on which a workpiece to be machined by a wire electric discharge machine is placed, and first, under a state serving as a reference, a distance between these two contact detection jigs (a reference distance) is measured by bringing the wire electrode into contact with these contact detection jigs. Subsequently, in a state of actual use, the wire electrode is brought into contact with these contact detection jigs in the same manner, so that a distance between these two contact detection jigs (an actual distance) is measured. Then, based on the difference between the reference distance and the actual distance, the amount of compensation is obtained to compensate an instruction for moving the wire electrode with respect to the table.